Yes ya lazy git do at least 500
Sounds like you need some protein man. I was doing 200 a day locked up at 140 lbs
You don't have a lot to push up. :P Bulk up, train down, Bulk up, train down.
Learn Krav Maga. Need to learn to defend yourself at that height and weight. And for your confidence. Push-ups are nice but like a band aid on a cancerous tumor.
Your body will answer that question for you. You should give your body rest though. Do you feel sore? Those are micro-fissures in the muscle. Tiny tears/cuts. You need to let those heal, or you'll just have muscles full of scar tissue. Also, with back issues, sit-ups aren't the best idea. Core exercises will give you greater benefit with less stress on your back.
Idk I like army guys way:D
pressups are easy, you don't really need strength to do them, try pullups you weakling.
pressups are pushups lol. I was joking anyway. You do plenty
Bro... Do you even lift?